1. Field of the Invention
The present invention relates to an apparatus and a method for determining a messages transmission period in an elevator group control system which includes a plurality of elevator controllers, a separate group controller and a serial communication bus line connecting the plurality of elevator controllers with the group controller, so that a load on a communication line is reduced and a data transmitting speed is improved when the messages are transmitted between the elevator controllers and the group controller.
2. Description of the Conventional Technology
In the elevator group control system, generally, the group controller and the elevator controllers are connected in 1:1 parallel fashion to perform serial communications. Thus, the load on the communication line is not heavily burdened when there are a large number of elevator controllers.
However, as each elevator controller is connected with the group controller through each exclusive cable, this kind of communication system has the problem that the number of cable in the communication line are too many. Under the circumstances, it has been disclosed a serial communication system wherein a plurality of elevator controllers are associated with the group controller through a serial communication bus line. However, in a case of using the serial communication bus line, the load on the communication line is apt to be heavily burdened when data are transmitted at once from each elevator controller.
Moreover, in the conventional group controller, the data transmission period of the elevator controller is fixedly determined without consideration of the number of elevator controllers connected thereto. Namely, if the time it takes for one of the elevator controllers to use the serial communication bus line is determined as 10 ms in a predetermined period and eight elevator cars can be associated with the group controller through the serial communication bus line, the time assigned to the whole elevator controllers is 80 ms. If the number of elevator cars associated with the group controller is four, the data transmission is performed during 40 ms among the predetermined total time (80 ms) that the elevator controllers are able to use the serial communication bus line assigned thereto. Therefore, this causes a problem of a non-efficiency by spending a time of 40 ms. Such a conventional technology will be explained below:
FIG. 1 shows a block diagram illustrating the whole constitution of a conventional group controller of an elevator car. As shown in FIG. 1, the conventional group controller includes an operation controlling section 11A for sensing an occurrence of failure in an elevator controller and for controlling specific operations; a statistics processing section 11B for collecting and arranging various statistics data to evaluate operation conditions of a group controller 11; a traffic information analyzing section 11C for collecting the present data to predict a communication load to the communication signals in the process that the group controller 11 assigns an optimal elevator car, and storing the data in a traffic information data base 11D; a hall call registration table 11E for storing hall button input signals created in each elevator landing floor; a hall call assignment table 11F for storing the optimal elevator car assigned by the group controller 11 in response to the input hall call; a hall call assignment section 11G for assigning an optimal control operation in response to the corresponding hall call by checking the operation conditions of each of elevator controllers 12A-12K when a hall call is created, and on the basis of the determination results, assigning the optimal elevator car to the created hall call; a data receiving section 11H and a data transmitting section 11I for performing the data communication; and a data accumulating section 13 for collecting the data transmitted from a number of the elevator controllers 12A-12K and transmitting them to the data receiving section 11H through the serial communication bus line, and transmitting the data provided through the data transmitting section 11I to the corresponding landing floor controllers 14A-14M and 15A-15M.
The operation of the conventional group controller as disclosed above will be explained with reference to FIGS. 1 to 3 as follows.
The transmitted data created from each of the elevator controllers 12A-12K are received through a routine as shown in FIG. 2. If a user selects an operation bottom for an elevator car and power is supplied into each of the elevator controllers 12A-12K, an initialization is executed and then an operability of an elevator controller is discriminated in test SA1. If the elevator controller is in a normal condition, the memory in the elevator controller is initialized. That is, the necessary functions are executed such as clearing the memory of RAM, transmitting the data stored in ROM into RAM, and assigning addresses. Thereafter, the programs required for elevator controllers are started and the data transmitting/receiving programs are also started so that the data created from the elevator controllers can be transmitted to the group controller.
In the elevator controllers 12A-12K connected with the group controller 11, the intervals in which the data transmitting/receiving programs are started, are not constant since all of their operation conditions cannot be recognized. This is because the time for users to supply the elevator controller with the power is the point which the data transmitting/receiving programs of the elevator controllers are started. These conditions will be explained referring to the drawings as follows:
FIG. 3 shows a timing diagram for transmitting the messages created from each of the elevator controllers according to the conventional technology.
In FIG. 3, regarding a time at which a data transmission program starts, if the first elevator controller 12A starts after 5 ms from an optical start time; the second elevator controller 12B after 10 ms; the third elevator controller 12C after 15 ms; the fourth elevator controller 12D after 20 ms; and the fifth elevator controller 12E after 30 ms, respectively, and if the data transmission period is determined as 50 ms in each of elevator controllers 12A-12K, the data transmitted from the third elevator controller 12C at a point of 17 ms is delayed since the second elevator controller 12B has already occupied the serial communication bus line.
Herein, the period in which the data transmission program starts in elevator controllers 12A-12K, that is, data transmission period of 50 ms is the minimum period in which the group controller has to receive the information for operation conditions of the elevator car from each of elevator controllers 12A-12K in order to successfully perform the whole elevator control. Namely, in order that the group controller 11 can complete a successful performance of the group operation, the data should be received within 50 ms from all elevator controllers 12A-12K.
The data transmission period in each of elevator controllers 12A-12K is the fixed value to be predetermined in the program. As the data transmission period has the fixed value of 50 ms, which is designated by the user, in case that the number of elevator controllers associated with the group controller 11 is four and that each of elevator controllers 12A-12K transmits data for 10 ms, it will take only 40 ms to use the serial communication line assigned to the elevator controller.
In such a manner, there is the problem that the communication line becomes heavily burdened by transmitting the data to the serial communication bus line nearly at the same time since the communication method between the conventional group controller and elevator controllers is determined by the period in which the data transmission programs of elevator controllers start, that is, the time that the data transmission programs supply the elevator controllers with power.
Further, the data transmission period of each elevator controller (i.e. the period in which each elevator controller uses the serial communication bus line) is predetermined on the program without consideration of the number of elevator controllers connected to the serial communication bus line. Consequently, if the number of elevator cars is determined under a maximum value of number which can be associated, there is the problem of non-efficiency in the communication line such that time-wise, the optimal operation of the serial communication line by the elevator controllers is not achieved.